Ymir was the oldest and most powerful of the Ice Giants, an otherdimensional race of enormous humanoid creatures. The huge size, durability, and colossal strength of the Ice Giants made them formidable foes to the gods of Asgard over the millennia.
Ymir was the progenitor of the entire race of Ice Giants as well as the Frost Giants, although he differed considerably in appearance from many of his current descendants, such as Utgard-Loki. Ymir and many of the first members of his race were also known as Ice Giants. Like the other Ice Giants, Ymir was covered with snow and ice, and constantly generated intense coldness from his body. The later generations of Ymir's race, such as Utgard-Loki, did not generate cold, and were not covered with ice and snow, and were therefore known simply as Frost Giants. Nonetheless, the great size of the Frost Giants was dependent on cold temperatures, and members of the later generations of Frost Giants, unable to create coldness from their own bodies, would shrink in size if exposed to sufficient heat. Continued exposure to such heat would melt such a Frost Giant entirely.
Except for the fire demon Surtur, Ymir was the oldest known being in the "Nine Worlds" of the Asgardian cosmology. It was said that millennia ago warm air from the otherdimensional realm of fire, Muspelheim, crossed a dimensional barrier into the location of the magical Well of Life, Tons of ice from Niffleheim, the otherdimensional realm of ice and cold, formed above the Well of Life. It was said that in time the warm air from Muspelheim caused these tons of ice over the Well to transform into the living, sentient Frost Giant Ymir. Another being appeared from the ice, the enchanted cow Audumla. Audumla fed off the ice itself, and Ymir subsisted on the milk Audumla produced. Some claimed that Ymir's first child was a female named Atali.
Ymir went to live in Niffleheim, which he populated with the race of Ice Giants. (The more recent generations of Frost Giants lived instead in the realm of Jotunheim.) At some point before 10,000 BCE, humans began to worship Ymir and his first daughter as deities. Among these humans were the Vanir people whose members would include Ulysses Bloodstone, Niord Worm's Bane, and possibly Raa and the Maha Yogi. Legends tell of Ymir imprisoning a group of vampires. The young god Odin and his brothers Vili and Ve fought a war with the Ice Giants and slew Ymir. According to Asgardian legend, Odin, Vili, and Ve created the Earth and sky from Ymir's corpse, but this part of the story is clearly untrue.
Ymir, however, succeeded in regenerating himself, and led the Ice Giants in war against Asgard at some later time. Odin created a chasm containing an interdimensional nexus through which Ymir's army plunged into Muspelheim, where the native demons took the Giants prisoners. Odin then entrapped Ymir himself within a circle of flame within a volcanic area. It is not known how long Ymir remained there.
In recent times a member of the mystical cult called the Sons of Satannish used the so-called Spell of Fire and Ice to bring both Ymir and Surtur to Earth, where they began wreaking havoc. Earth's Sorcerer Supreme, Doctor Stephen Strange, used the Crystal of Conquest, which contained part of the mystical power of the demons known as Santannish and Mephisto, to transport Surtur and Ymir magically into each other's presence at the very instant they were lashing out with their weapons. Ymir and Surtur thus struck each other's weapons, creating a mystical "implosion" in which each being temporarily cancelled out the powers of the other, and each was returned to his home dimension, Surtur to Muspelheim and Ymir to Niffleheim.
Ymir possesses vast superhuman strength, greater than that of any other Frost or Ice Giant. He is extremely long-lived, and possibly immortal. His body greatly resembles ice in various ways, and if it was not for his ability to generate intense cold from his body, Ymir would melt when exposed to high temperatures. Ymir's body is extraordinarily resistant to injury, and although it can be shattered, as ice can, Ymir can cause the fragments of his form to reassemble.
Ymir continually generates extreme cold from his body in an unknown, perhaps magical fashion. If he so chooses, Ymir can cause anything he touches, including the air, to freeze.